Communication systems exist which allow a live voice and/or video call to be conducted between two or more end-user terminals over a packet-based network such as the Internet, using a packet-based protocol such as internet protocol (IP). This type of communication is sometimes referred to as “voice over IP” (VoIP) or “video over IP”.
To use the communication system, each end user first installs a client application onto a memory of his or her user terminal such that the client application is arranged for execution on a processor of that terminal. To establish a call, one user (the caller) indicates a username of at least one other user (the callee) to the client application. When executed the client application can then control its respective terminal to access a database mapping usernames to IP addresses, and thus uses the indicated username to look up the IP address of the callee. The database may be implemented using either a server or a peer-to-peer (P2P) distributed database, or a combination of the two. Once the caller's client has retrieved the callee's IP address, it can then use the IP address to request establishment of a live voice and/or video stream between the caller and callee terminals via the Internet or other such packet-based network, thus establishing a call. An authentication procedure is typically also required, which may involve the user providing credentials via the client to be centrally authenticated by a server, and/or may involve the exchange of authentication certificates between the two or more users' client applications according to a P2P type authentication scheme.
With the increasing prevalence of electronic devices capable of executing communication software, both around the home and in portable devices on the move, then it is possible that multiple different terminals may be available at one end of the call, each having audio and/or video inputs and each of which could potentially be installed with an instance of the client application. In such cases it may be desirable to consider how best exploit these multiple resources to maximise the usefulness of the communication system.
Further, there are some existing arrangements that provide a remote interface for a call. For example Bluetooth headsets provide an input/output interface that is remote from the phone that handles the call. DECT phones (Digital Enhanced Cordless Telephones) provide handsets that are remote from the base station. There also exists a video application, running on a smart phone, and showing up on a computer as a video device in the list of video devices (such that it can be used e.g. in a VoIP client by simply selecting it in the video device list).